diff --git a/src/backend/libpq/ip.c b/src/backend/libpq/ip.c
index 9591ed28624..d490a82e72a 100644
--- a/src/backend/libpq/ip.c
+++ b/src/backend/libpq/ip.c
@@ -240,7 +240,7 @@ getnameinfo_unix(const struct sockaddr_un * sa, int salen,
 				 char *service, int servicelen,
 				 int flags)
 {
-	int			ret = -1;
+	int			ret;
 
 	/* Invalid arguments. */
 	if (sa == NULL || sa->sun_family != AF_UNIX ||
@@ -250,14 +250,14 @@ getnameinfo_unix(const struct sockaddr_un * sa, int salen,
 	if (node)
 	{
 		ret = snprintf(node, nodelen, "%s", "[local]");
-		if (ret == -1 || ret > nodelen)
+		if (ret < 0 || ret >= nodelen)
 			return EAI_MEMORY;
 	}
 
 	if (service)
 	{
 		ret = snprintf(service, servicelen, "%s", sa->sun_path);
-		if (ret == -1 || ret > servicelen)
+		if (ret < 0 || ret >= servicelen)
 			return EAI_MEMORY;
 	}
 
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index 77dbf4f92ff..8bdd5d0021e 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -4070,7 +4070,7 @@ get_dbstat_filename(bool permanent, bool tempname, Oid databaseid,
 					   pgstat_stat_directory,
 					   databaseid,
 					   tempname ? "tmp" : "stat");
-	if (printed > len)
+	if (printed >= len)
 		elog(ERROR, "overlength pgstat path");
 }
 
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 0b403a32729..f33160bf69c 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -9047,6 +9047,8 @@ do_serialize(char **destptr, Size *maxbytes, const char *fmt,...)
 	if (*maxbytes <= 0)
 		elog(ERROR, "not enough space to serialize GUC state");
 
+	errno = 0;
+
 	va_start(vargs, fmt);
 	n = vsnprintf(*destptr, *maxbytes, fmt, vargs);
 	va_end(vargs);
diff --git a/src/interfaces/ecpg/pgtypeslib/common.c b/src/interfaces/ecpg/pgtypeslib/common.c
index 7adca66618d..998764d6627 100644
--- a/src/interfaces/ecpg/pgtypeslib/common.c
+++ b/src/interfaces/ecpg/pgtypeslib/common.c
@@ -110,7 +110,7 @@ pgtypes_fmt_replace(union un_fmt_comb replace_val, int replace_type, char **outp
 						break;
 				}
 
-				if (i < 0)
+				if (i < 0 || i >= PGTYPES_FMT_NUM_MAX_DIGITS)
 				{
 					free(t);
 					return -1;
diff --git a/src/port/getaddrinfo.c b/src/port/getaddrinfo.c
index 90c1b877eb4..d04865284e2 100644
--- a/src/port/getaddrinfo.c
+++ b/src/port/getaddrinfo.c
@@ -404,7 +404,7 @@ getnameinfo(const struct sockaddr * sa, int salen,
 			ret = snprintf(service, servicelen, "%d",
 						   ntohs(((struct sockaddr_in *) sa)->sin_port));
 		}
-		if (ret == -1 || ret >= servicelen)
+		if (ret < 0 || ret >= servicelen)
 			return EAI_MEMORY;
 	}
 
diff --git a/src/test/isolation/isolation_main.c b/src/test/isolation/isolation_main.c
index a0bd92f3747..a41aeeb834f 100644
--- a/src/test/isolation/isolation_main.c
+++ b/src/test/isolation/isolation_main.c
@@ -73,15 +73,27 @@ isolation_start_test(const char *testname,
 	add_stringlist_item(expectfiles, expectfile);
 
 	if (launcher)
+	{
 		offset += snprintf(psql_cmd + offset, sizeof(psql_cmd) - offset,
 						   "%s ", launcher);
+		if (offset >= sizeof(psql_cmd))
+		{
+			fprintf(stderr, _("command too long\n"));
+			exit(2);
+		}
+	}
 
-	snprintf(psql_cmd + offset, sizeof(psql_cmd) - offset,
-			 "\"%s\" \"dbname=%s\" < \"%s\" > \"%s\" 2>&1",
-			 isolation_exec,
-			 dblist->str,
-			 infile,
-			 outfile);
+	offset += snprintf(psql_cmd + offset, sizeof(psql_cmd) - offset,
+					   "\"%s\" \"dbname=%s\" < \"%s\" > \"%s\" 2>&1",
+					   isolation_exec,
+					   dblist->str,
+					   infile,
+					   outfile);
+	if (offset >= sizeof(psql_cmd))
+	{
+		fprintf(stderr, _("command too long\n"));
+		exit(2);
+	}
 
 	pid = spawn_process(psql_cmd);
 
diff --git a/src/test/regress/pg_regress.c b/src/test/regress/pg_regress.c
index 15690177e0f..8a782324453 100644
--- a/src/test/regress/pg_regress.c
+++ b/src/test/regress/pg_regress.c
@@ -998,7 +998,7 @@ config_sspi_auth(const char *pgdata)
 	} while (0)
 
 	res = snprintf(fname, sizeof(fname), "%s/pg_hba.conf", pgdata);
-	if (res < 0 || res >= sizeof(fname) - 1)
+	if (res < 0 || res >= sizeof(fname))
 	{
 		/*
 		 * Truncating this name is a fatal error, because we must not fail to
diff --git a/src/test/regress/pg_regress_main.c b/src/test/regress/pg_regress_main.c
index d9591c0608c..df4f01bf372 100644
--- a/src/test/regress/pg_regress_main.c
+++ b/src/test/regress/pg_regress_main.c
@@ -60,16 +60,28 @@ psql_start_test(const char *testname,
 	add_stringlist_item(expectfiles, expectfile);
 
 	if (launcher)
+	{
 		offset += snprintf(psql_cmd + offset, sizeof(psql_cmd) - offset,
 						   "%s ", launcher);
+		if (offset >= sizeof(psql_cmd))
+		{
+			fprintf(stderr, _("command too long\n"));
+			exit(2);
+		}
+	}
 
-	snprintf(psql_cmd + offset, sizeof(psql_cmd) - offset,
-			 "\"%s%spsql\" -X -a -q -d \"%s\" < \"%s\" > \"%s\" 2>&1",
-			 bindir ? bindir : "",
-			 bindir ? "/" : "",
-			 dblist->str,
-			 infile,
-			 outfile);
+	offset += snprintf(psql_cmd + offset, sizeof(psql_cmd) - offset,
+					   "\"%s%spsql\" -X -a -q -d \"%s\" < \"%s\" > \"%s\" 2>&1",
+					   bindir ? bindir : "",
+					   bindir ? "/" : "",
+					   dblist->str,
+					   infile,
+					   outfile);
+	if (offset >= sizeof(psql_cmd))
+	{
+		fprintf(stderr, _("command too long\n"));
+		exit(2);
+	}
 
 	pid = spawn_process(psql_cmd);